Various types of viscous fluids are used in industrial processes. For example, viscous fracturing fluids are used to enhance production of oil and gas (hydrocarbons) from wells in which the subterranean pressure has declined.
When oil and/or gas are removed from a subterranean formation through drilling, the pressure in the formation declines. As a result of the pressure decline, the production of oil and/or gas from the well also declines. Although oil and/or gas may still be present in the formation, production may decrease to such an extent that further removal of oil and/or gas becomes uneconomical. In such cases, it is crucial to extract as much oil and/or gas from the formation as possible. Production from formations in which the pressure has declined may be raised by techniques generally known as well stimulation. To stimulate an oil and/or gas well, a fracturing fluid, consisting of a viscous slurry—typically incorporating a suspended guar polymer (and other additives) in a carrier fluid—along with other chemical additives—is injected into the formation, under high pressure, via the well's bore hole. By applying hydraulic pressure within the formation, the fracturing fluid fractures the subterranean strata surrounding the bore hole, thereby increasing and extending the area from which oil and/or gas may be drained. Once a fracture is induced, a propping agent, such as sand, is added to the slurry, causing the fracture to remain open after the slurry is removed. After the desired amount of proppant has been placed in the fractured formation, pumping is terminated, the slurry is chemically “broken” and removed, and the well is shut-in for a time. Later, the well is reopened in order to recover the oil and/or gas through the fractures thus created.
To be effective in the fracturing process, the slurry used in the fracturing fluid must have certain chemical properties and must be maintained under certain conditions. For example, depending upon the nature of the subterranean formation to be fractured and other down-hole characteristics of the well (such as temperature), the slurry must have a certain viscosity and pH before it can be used, the specific viscosities, pH and other properties of the slurry being unique—and often proprietary—to the fracturing fluids employed by each pumping service company. Otherwise, the slurry may be ineffective for its intended purpose. It may also cause equipment malfunctions, such as the clogging of pumps and hoses. Moreover, there has to be enough field-ready slurry on-hand for the intended fracturing application, else lengthy delays and costly downtime may result. Mixing adequate quantities of consistently high quality slurry in the field has always been difficult and time-consuming. It is therefor important to the oil and gas well pressure pumping services industry that appropriate slurries be delivered and maintained in “field ready” condition, improving not only product performance, but also field efficiencies.
One way to ensure that a sufficient quantity of field-ready slurry is always available is to store pre-mixed, field-ready slurries in one or more tanks, either on the drilling site or close thereto. The slurry may then be pumped from the tanks (or transported a short distance and pumped from the transport) to the well bores as needed. When the slurry supply becomes low, a slurry manufacturing and supply company, such as Benchmark Energy Products, L.P., of Houston, Tex., may be called upon to replenish the slurry. The slurry supply company delivers the new slurry in a “field ready” condition to the tank site, typically using one or more tanker trucks. The frequency with which the slurry supply company delivers the new slurry depends on several factors, including the size of the local tanks, the rate of usage, and other similar factors.
A drawback of the above arrangement is that it is an entirely manual process. Usually, one or more persons have to physically gauge and monitor the level of the slurry in the tanks and alert the slurry manufacturing and supply company when the level becomes low. In addition, the condition of the slurry in the tank(s) also has to be monitored to ensure the slurry remains “field ready.” Over time, the slurries are susceptible to degradation—particularly settlement of the suspended polymer, especially at extreme temperatures—if not periodically (re)mixed. Depending on the number of slurry storage tanks in use, these constant monitoring and mixing tasks may significantly strain the available technical and personnel resources, and, if not properly attended to, lead to product waste, or worse, to job failures. The mechanical components of the slurry storage system (such as the tanks, pumps, compressors, mixers, and valves) must also be constantly monitored and maintained to ensure operational integrity and prevent spills and leaks that could lead to environmental contamination.
Accordingly, what is needed is way automate the above process. In particular, what is needed is a way to continuously monitor both the quantities and the condition of the slurry in multiple tanks, at local as well as remote storage sites, from a single centralized location, to remotely direct the re-mixing of the slurry, if and when necessary, and to automatically re-supply the customer on as “as need” basis, thereby ensuring that an adequate supply of high quality, “field ready” slurry is available at all times.